I have XP on my second drive sdb and just installed sabayon onto the first drive sda. When I tried to boot XP through grub it just hangs. Booted sabayon instead and out of curiosity checked out my second drive and found that almost all of my data had gone, including windows!
I made sure to select the right drive during sabayon install.
Surely this isn't possible as windows was on a seperate drive unrelated to sabayon, as a noob to all this I am unsure whether this is a grub issue or I lost all of my data

I'm not crazy, at least I think so .
There's clearly a relationship between me installing Sabayon and losing information on the seperate drive.
I suspect the information is still there but something mysterious has happened.

EDIT: Is it possible that grub has somehow damaged the MBR on my second drive?
Could that damage my XP file system?!
Is the moon made of cheese?

How are you trying to boot XP? if grub os on sda (the drive with Sabayon), and XP is on sdb and your trying to boot XP via grub you need to make sure Sabayon mapped windows properly. Loop1 didn't setup grub right to boot XP on a second hdd, I had to manually add the correct parameters.

Got a little further by using that mapping trick but then it hangs again, HD indicator stays lit but no HD activity can be heard. There may possibly be a corruption/hardware issue that only shows up when trying to install a second OS as this has happened twice now. Install linux and loss of data on second drive. It's certainly a strange one

I only really need to recover my login details from roboform, any recommendations on a linux based fat32 recovery program

Correctly mapping the drives is a possible solution - the easiest way out for you, I believe is to keep your XP on the first bootable disk and re-install Linux and have it put Grub onto the MBR, this will automatically put evrything in one place. The only caveat is that you cannot re-install, or repair XP without disturbing Linux - but even that is manageable.

Ah ha! Funnily enough, something odd happened to my XP install also. This was after I installed openSuse 10.2. The partition table changed, so that the linux partition was marked as bootable (grub does this). This was enough to trigger windows into trying to rename its drives. So, what was once the XP system on "J:" had become "C:" and so forth. Unfortunately, windows tries to assign drive letters to partitions it doesn't understand, although you never see them. By the time I had noticed what had happened, it was too late. Removing the bootable flag did not help, as windows had already "seen" the change. No matter what I did, I couldn't get it to boot (even to safe mode), it would just hang. Eventually fixed by backing up the non-windows partitions and changing them all to FAT32 (and this was after a reinstall of windows too!). Then you use the drive rename utility in windows to reassign all the drives, and put things back the way they were.

In retrospect, I think there is some place in the registry that maintains these assignments. I'm sure I saw something when I was fishing about. So, for future occurrences, the wine registry editor could be a valuable tool.

This will, unsurprisingly, fix your MBR.
You should then be able to boot into XP but Sabayon will have apparently gone (but it hasn't really).
Then boot up from your Sabayon disk and go through the install again. At some point (I can never remember where) it gives you the option of repairing Grub. You can then put Grub on your MBR and all will be well

& from there it just hangs, I have to ctl+alt+del to be able to choose SL. After that, SL boots fine. I've tried the live DVD of SL 3.4 x86-64, & attempting to repair grub without any success Originally, I had my XP install on the 160GB & SL on the 80GB. I'll try to fixmbr tonight then, any other thoughts?